Steering and Driving Systems and Related Vehicles

ABSTRACT

A ZTR vehicle includes true or proper ZTR steering in the forward and reverse directions. The vehicle has independently driven locomotive drives that drive the wheels to provide mobility and steering to the vehicle. A steering wheel is included that pivots one of two steering input members that rotate to independently shift the drive units. A speed and direction pedal is also included, which is communicated to provide direction and magnitude input to the drive units. The steering input and speed and direction inputs coordinate propelling the vehicle such the vehicle turns in the same direction when traveling forward as well as in reverse.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a continuation of co-pending U.S. patentapplication Ser. No. 11/269,899, filed Nov. 8, 2005 which is acontinuation of U.S. patent application Ser. No. 10/245,158, filed Sep.11, 2002, now issued as U.S. Pat. No. 6,962,219, which claims priorityto U.S. Provisional Application Ser. No. 60/322,943, filed on Sep. 17,2001. U.S. patent application Ser. Nos. 10/245,158 and 11/269,899 areincorporated by reference.

BACKGROUND OF THE INVENTION

A. Field of Invention

The present invention relates to the art of Zero Turn Radius vehiclesand more specifically to Zero Turn Radius mowers incorporatingmechanical steering systems.

B. Description of the Related Art

Zero Turn Radius (ZTR) vehicles including mowers work well for theirintended purpose. One advantage of ZTR vehicles is that they are capableof making very tight (zero radius) turns. One disadvantage of most ZTRvehicles is that their operation is not intuitive for most operatorsbecause steering of the vehicles is accomplished by steering levers,rather than a steering wheel. Recently, steering wheels have beenincorporated onto ZTR vehicles. However, known ZTR vehicles using asteering wheel steer the vehicle differently in the forward direction oftravel than in reverse. That is to say, that with the steering wheelsteered to turn the vehicle right, and upon depressing the accelerator,the vehicle will make a forward right turn. But, when the accelerator isdepressed to drive the vehicle in reverse, the vehicle makes a rearwardleft turn, rather than a rearward right turn. What is needed is areliable mechanical ZTR steering system that steers the vehicleconsistently in the direction that the steering wheel is turned inforward as well as the reverse directions.

Other objects and advantages of the invention will appear from thefollowing detailed description of the preferred embodiment of theinvention with reference being made to the accompanying drawings.

BRIEF SUMMARY

The present invention includes a ZTR vehicle that provides for propersteering of the ZTR vehicle in the forward and reverse directions.

Another aspect of the present invention includes a ZTR vehicle having asteering wheel that controls the steering of the vehicle.

Yet another aspect of the present invention includes hydrostatic drivesthat drive each respective rear ground engaging wheel independently fromthe other.

Still another aspect of the present invention includes an asynchronouslyactuated set of two steering input members that engage the hydrostaticdrives.

Still yet another aspect of the present invention includes a speed anddirection input member that maneuvers pintle links of the hydrostaticdrive substantially in unison.

A ZTR vehicle is provided that steers the same in the forward andreverse directions. The vehicle includes a steering wheel operativelyconnected to independently steer two (2) drive control members. Thedrive control members provide input to two (2) locomotive drive unitsthat propel and steer the vehicle. An accelerator pedal or speed inputdevice is rotatably disposed about the vehicle to provide speed anddirection input to drive the vehicle. The accelerator pedal is connectedto a rotating shaft that pivots two (2) speed input members. Thesteering wheel provides steering input to two (2) steering inputmembers. The steering input members each have sleeves that slidelongitudinally about the drive control members to provide independentshifting of the drive control members in the forward and reversedirections.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangement ofparts, a preferred embodiment of which will be described in detail inthis specification and illustrated in the accompanying drawings whichform a part hereof and wherein:

FIG. 1 is a side view of a ZTR vehicle.

FIG. 2 is a partial cutaway view of the power train of the ZTR vehicle,including Hydrostatic Drives.

FIG. 3 is a top view of the mechanical ZTR control linkage.

FIG. 4 is a close up side view of the mechanical ZTR control linkage.

FIG. 5 is a perspective view of the steering wheel and steeringmechanism.

FIG. 6 a is a schematic side view of the ZTR control assembly with nosteering input and no speed input.

FIG. 6 b is a schematic side view of the ZTR control assembly with nosteering input and speed input driving the vehicle in a forwarddirection.

FIG. 6 c is a schematic side view of the ZTR control assembly with nosteering input and speed input driving the vehicle in a reversedirection.

FIG. 7 a is a schematic side view of the ZTR control assembly with thesteering wheel fully turned and no speed input.

FIG. 7 b is a schematic side view of the ZTR control assembly with thesteering wheel fully turned and speed input actuated to drive thevehicle in forward direction resulting in a forward ZTR turn.

FIG. 7 c is a schematic side view of the ZTR control assembly with thesteering wheel fully tuned and speed input actuated to drive the vehiclein reverse direction resulting in a reverse ZTR turn.

FIG. 8 is schematic representation of the drive control members and thespeed input members engaged in the forward direction.

FIG. 9 is schematic representation of the drive control members and thespeed input members engaged in the reverse direction.

FIG. 10 is schematic representation of the drive control members and aseries of trajectories for the control members.

FIG. 11 a is schematic representation of the drive control members andthe speed input members engaged in the forward direction.

FIG. 11 b is schematic representation of the drive control members andthe speed input members engaged in the forward direction.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein the showings are for purposes ofillustrating a preferred embodiment of the invention only and not forpurposes of limiting the same, FIG. 1 depicts a ZTR vehicle 1. The ZTRvehicle 1 includes a frame 3 supporting two rotatably-mounted frontground engaging wheels 4, 5 and two rotatably-mounted rear groundengaging wheels 6, 7. The rear ground engaging wheels 6, 7 providesteering and mobility to maneuver the vehicle 1 as desired. The vehicle1 may include an engine 7, which may be an internal combustion engine 8.However, any type of engine may be chosen with sound engineeringjudgment that provides power to operate the vehicle 1. The vehicle 1 mayalso include a steering wheel 10 that is operatively connected to steerthe vehicle 1 as will be discussed in greater detail in a subsequentparagraph. A speed control member 11 may be rotatably attached to thevehicle 1, which is operable to provide variable speed control input infirst and second directions, as will be discussed subsequently.Additionally, the ZTR vehicle 1 may include a mower deck 13 wherein theZTR vehicle 1 is a ZTR mower 2.

With reference now to FIG. 2, a pair of locomotive drive units, 16, 18are shown operatively connected to drive rear ground engaging wheels 6,7 respectively. In the preferred embodiment, the drive units 16, 18 arehydrostatic drives (HDs) but it is to be understood that other driveunits are also contemplated, such electric and mechanical drive units.The drive units 16, 18 are used to independently drive the rear wheels6, 7 as is well known for ZTR vehicles and which will not be discussedfurther. The hydrostatic drives 16, 18 may include pivotally attachedpintle links 22, 24 that when pivoted in first and second directionscontrol power that drives the respective wheels in first and seconddirections. The more that the pintle links 22, 24 are pivoted, thegreater the magnitude of speed that the locomotive drives 16, 18 aredriven in each respective direction. First ends 26 a, 28 a of inputshafts 26, 28 may be connected to the pintle links 22, 24 respectivelyand may translate tension and compression forces for use in pivoting thepintle links 22, 24 in the first and second directions. It is noted thatthe input shafts 26, 28 may be independently shifted with respect to theother. By “shifted” it is meant that the input shafts 26, 28 may beseparately longitudinally moved whereby the pintle links 22, 24 arepivoted respectively. Additionally, the input shafts 26, 28 may bepivotally attached at the first ends 26 a, 28 a to the pintle links 22,24 in such a manner so as to allow for pivotal movement of the inputshafts 26, 28 with respect to the pintle links 22, 24. In other words,the first ends 26 a, 28 a of the input shafts 26, 28 may be pivoted withrespect to the pintle links 26, 28.

With reference now to FIGS. 2 and 3, a ZTR control assembly is showngenerally at 31. The ZTR control assembly 31 includes a linkage, whichin the preferred embodiment may be mechanical members, interconnected toreceive steering input from the steering wheel 10 and speed controlinput from the speed control member 11 for use together in providingcontrol to shift the input shafts 26, 28. The speed control member 11may be a foot pedal or hand lever for controlling the magnitude anddirection of the speed input by pivoting the member 11. It is noted thatany member may be used to provide speed input as chosen with soundengineering judgment. The steering wheel 10 may also be exchanged withother steering members as is appropriate for use with the presentinvention. The linkage 31 is configured to steer the vehicle the same inthe forward as in the reverse direction. In other words, the ZTR controllinkage 31 is interconnected to the steering wheel 10 and the speedcontrol member 11 to provide proper steering in the reverse and forwarddirections of travel. That is to say that when the vehicle is beingdriven in a first, or forward, direction and when the steering wheel 10is turned in a first steering direction, to the right for example, theleft rear ground engaging wheel will drive faster than the right rearground engaging wheel thereby steering the vehicle in the firstdirection, or right direction. For true ZTR steering in this case, theleft rear ground-engaging wheel may drive forward and the right rearground-engaging wheel may drive backward. When the vehicle is driven inthe reverse, or second, direction, and with the steering wheel stillturned in the first steering direction, which may be to the right, theleft rear ground-engaging wheel may still drive faster than the rightrear ground engaging wheel accept in the opposite direction causing thevehicle to steer properly in the forward and reverse direction. Bysteering properly in the forward and reverse directions it is meant thatthe steering of the ZTR vehicle responds similarly to a vehicle havingdrive wheels driven at a constant rate and wherein steering wheels arepivoted with respect to the frame of the vehicle.

With continued reference to FIGS. 2 and 3, the ZTR control linkage 31may include a rod member 38 that is rotatably attached with respect tothe frame 3. The rod member 38 has a first end 39 that is fixedlyattached to a speed control member 11 or pedal member 41. The pedalmember 41 is therefore also pivotally attached with respect to the frame3, which is allowed to rotate in first and second directions. It isnoted the pedal member 41 may be biased via a spring or other mechanismtoward a neutral or non-driving position. The first direction mayrepresent the forward direction of travel, which when member 11 isdepressed will drive the vehicle forward. With the steering wheel notsteered in a first or second direction, the drive units will driveequally at the same magnitude propelling the vehicle straight forward,not steering in either direction. Likewise, the second or reversedirection functions in a similar manner. In this way, depressing thepedal member 41 in a first direction rotates the rod member 38 in afirst rotational direction 42 and likewise depressing the pedal member41 in a second direction rotates the rod member 38 in a secondrotational direction 43. There is also fixedly attached to the rodmember 38 two control members 34, 35, which may be two speed inputmembers 54, 55. However, in that the two members 34, 35 rotate togetherin unison, the two control members 34, 35 may function as a singlespeed-control member 34 a. In this way, actuation of the pedal member 41applies rotational force equally to both of the speed input members 54,55. The speed input members 54, 55 will be discussed in greater detailin a subsequent paragraph. The ZTR control assembly 31 may also includetwo second members 44, 45, which may be steering input members 64, 65.The steering members 64, 65, at a first end 64 a, 65 a thereof, arereceived onto the rod member 38 in such a manner that the steeringmembers 64, 65 may rotate with respect to the rod member 38. In thisway, depressing the pedal member 41 in either direction does not affectthe rotational movement or adjustment of the steering members 64, 65.Additionally, there may be two generally tubular sleeve members 51, 52that are rotationally attached with respect to second ends 64 b, 65 b ofthe steering members 64, 65. The sleeve members 51, 52 are alsorespectively received onto the input shafts 26, 28 and may slidelongitudinally thereon for use in providing input steering forces aswill be discussed in a subsequent paragraph. As the steering members 64,65 are rotated, the sleeve members 64, 65 may independently rotate withrespect to the first ends 64 a, 65 a of the steering members 64, 65 andwill further be longitudinally adjusted along the input shafts 26, 28.

With reference now to FIGS. 3 and 4, FIG. 4 depicts a close up side viewof only one section of the mechanical ZTR control linkage 31 for thepurpose of clarity. It is understood that the opposite side of thelinkage functions in a similar manner. The rod member 38 has a U-shapedportion 38 a whereon the speed input members 54, 55 are fixedlyattached. The speed input members 54, 55 may have an aperture 36fashioned therein that receives the rod member 38. Subsequently, thespeed input members 54, 55 may be welded to the rod member 38 a.However, any configuration of the speed input member and any means offixedly securing the speed input members 54, 55 to the rod member 38 amay be chosen with sound engineering judgment. It is noted that FIG. 4shows the cross section of the U-shaped portion 38 a of the rod member38 disposed in the plane of the speed input members 54, 55. Likewise,FIG. 4 shows the cross section of the rod member 38 in the plane of thesteering members 64, 65 at the first end 64 a, 65 a of the steeringmembers 64, 65. Focusing on the input shafts 26, 28, the second ends 26b, 28 b are fashioned to form slot pins 58, 59. The slot pins 58, 59 arecurved so as to engage a slot 37 formed in the speed input members 54,55 as will be discussed in the following paragraphs. In this manner, theslot pins 58, 59 are fashioned to sliding engage the speed input members54, 55 along the length of the slot 37 formed in the speed input members54, 55. When the steering input 54, 55 are rotated in a first direction,the input shafts 26, 28 may be pulled or shifted in a first directionrotating the pintle links and engaging the driving units.

With continued reference to FIG. 4 and now to FIG. 5, the steering wheel10 may be fixedly connected to a pinion gear 70 that meshingly engages asteering disk 72 having coordinating gear teeth 73. At a distal end 75of the steering disk 72, the steering disk 72 is pivotally attached withrespect to the frame 3. In this manner, turning the steering wheel 10rotates the pinion gear 70 that in turn rotates the steering disk 72. Inthat the operation of steering wheels and steering mechanisms are wellknown, no further explanation will be offered at this point. First andsecond tension cables 77, 78 are further included and fixedly attach atfirst ends 77 a, 78 a to the steering disk 72, as clearly shown inFigures, and at second ends 77 b, 78 b to the steering members 64, 65.It is noted that the tension cables 77, 78 translate tension force only.In this way, rotating the steering wheel 10 applies force to only one ofthe tension cables 77, 78 at a time. In other words, rotating thesteering wheel 10 in a first direction applies tension force to tensioncable 77, while allowing tension cable 78 to be slack or be in a statehaving no tension applied to the cable. Consequently, rotating thesteering wheel 10 in the second direction applies tension force to cable78, while allowing cable 77 to be slack. In this manner, rotating thesteering wheel 10 applies tension force to one of the steering member64, 65. It is noted that the steering members 64, 65 may be biasedtoward a default position by any means chosen with sound engineeringjudgment. In this way, the steering member 64, 65 may be preloaded withpredetermined amount of force, taking up slack in the cables 77, 78during rotation of the steering wheel 10.

With continued reference to FIGS. 2 through 5 and now to FIGS. 6 and 7,the operation of the present invention will now be discussed. FIGS. 6and 7 schematically show the various positions of the steering members64, 65, the speed input members 54, 55 and the input shafts 26, 28 asrelated to steering and accelerating the vehicle 1. Specifically, FIG. 6refers to a first mode of operation where the vehicle 1 is drivingstraight, that is to say that the vehicle 1 is being driven forwardwithout steering input. In this mode, the driver depresses the pedalmember 41 (Reference FIG. 3) in a first direction 42, which causesrotation of the speed input members 54, 55. This is clearly depicted inFIG. 6 b. As previously described, this action results in the pintlelinks 22, 24 being shifted, which drives the vehicle 1 forward. It isnoted that the steering members 64, 65 remain in a constant defaultposition, which forces the slot pins 58, 59 toward one end 37 a of theslot 37. In a similar manner, depressing the pedal member 41 in thesecond direction 43 drives the vehicle 1 in reverse. Referring now toFIG. 7, FIG. 7 a shows the steering wheel 10 rotated in a firstdirection to a maximum position. In this manner, the tension cable 77applies force to rotate steering member 64, whereby the bias forceholding the steering member 64 is overcome. This shifts slot pin 58 to adistal end of slot 37. In this manner, depressing the pedal member 41 ina first direction causes rotation of pintle link 22 in a reversedirection than when slot pin 58 was biased in the default position. Inother words, depressing the pedal member 41 to drive the vehicleforward, with the steering wheel 10 fully turned in the first direction,causes pintle link 22 to drive that respective wheel in reverse. Notingthat the opposing wheel is driven forward, this results in a Zero Radiusturn. Thus, it can be seen that ZTR steering in forward and reverse isaccomplished. It is noted that the vehicle 1 may include front steerablewheels 4, 5 that are rotated proportionately to the turning radius ofthe vehicle. Any manner of steering the front wheels 4, 5 may be chosenwith sound engineering judgment. In this way, the front steerable wheels4, 5 may be rotated to be substantially tangent to an arc defined at onepoint by the radius of turning and by the other point at the center ofeach wheel 4, 5.

With reference again to FIG. 4 and now to FIGS. 8 and 9, the shifting ofthe input shafts 26, 28 will now be discussed. As previously mentioned,the input shafts 26, 28 may be rigid rods connected at respective firstends 26 a, 28 a to the pintle links 22, 24, reference FIG. 2. The pintlelinks 22, 24, as well known in the art, actuate the drive units, orstroke the hydrostatic drive, in first and second directions and atselectively varying magnitudes of speed. The distal ends of the inputshafts 26, 28, or drive control members, may be communicated to thespeed input members 54, 55 and the steering members 64, 65 as previouslydescribed. FIG. 8 shows only one of the speed input members 54, 55 andone drive control member or input shaft 26, 28 for clarity. The drivecontrol member 26, 28 may have a neutral or non-engaging position Nwherein the respective locomotive drive 16, 18 is substantially notengaged to drive in either the forward or reverse direction. The drivecontrol member 26, 28 is shown received in the slot 37 of the speedcontrol member 54, 55 at a top position 37 a. This may be the default orbiased position. When the pedal member 41 is rotated in a firstdirection 42, the drive control member 26, 28 is shifted in a firstdirection to engage the respective locomotive drive unit 16, 18 to drivein a first direction and speed. Similarly, FIG. 9 shows the same shiftedin a second direction. The first direction 42 may coordinate with aforward direction of travel and second direction 43 may coordinate withthe reverse direction of travel. However, any configuration of engagingthe drive units 16, 18 and shifting the control members 26, 28 may bechosen with sound engineering judgment.

It can be observed from FIGS. 8 and 9, that the drive control members26, 28 may be adjusted through the slot 37 applying a force F toovercome the bias force, which may be a spring force not shown,operatively connected in a manner well known in the art. In thepreferred embodiment, the force F may be applied via the slidablyengaging steering members 64, 65 actuated by selectively steering thesteering wheel 10, which will be discussed further in a subsequentparagraph. Continuing, the drive control members 26, 28 may selectivelypivot through the slot 37 to cross from a first direction 42 positionthrough the neutral position N to a second direction position 43. Thespeed input members 54, 55 may be rotated, in an analog fashion, at anypoint from a first maximum position 42 a to a second maximum position 43a establishing a series or a plurality of trajectories through which thedrive control members 26, 28 may be selectively maneuvered. FIG. 10shows one such series of trajectories. In this manner, the drive controlmembers 26, 28 may be selectively shifted from a top or upper slotposition to a lower or bottom slot position. However, it is expresslynoted that pivoting from the top to the bottom position may shift therespective drive control member 26, 28 from the first direction 42 tothe second 43 or from the second direction 43 to the first 42 dependingupon the position of the speed control members 54, 55. It is also notedthat the top and bottom positions of slot 37 may be selectivelypositioned at various points between the first and second maximumpositions 42 a, 43 a. In this way, as the speed input members 54, 55shift both of the drive control members 26, 28 in unison and in that thesteering members 64, 65 can be rotated independently or asynchronously,it can be seen that the shifting of the drive control members 26, 28 mayresultantly actuate the locomotive drives 16, 18 to steer and propel theZTR vehicle 1 in a manner consistent with proper steering in the forwardand reverse directions.

With reference now to FIGS. 11 a and 11 b, the drive control members 26,28 are shown steered in a first direction and driven in a firstdirection 42. For purposes of clarity, the steering members 64, 65 arereplaced with force vectors F1 to show the operation of the presentinvention more clearly. It should be noted that the presentconfiguration is representative of FIG. 7 c. In this case, the tensioncable 77, which may also be rigid rod members configured to translatetension force only, pull on the first rotatable steering members 64,overcoming bias forces, thereby rotating the steering member 64 in afirst direction, which may be clockwise. Since the opposing cable 78 isnot under tension, no steering force is supplied to the steering member65, although the steering member 65 may include a force means to biasthe steering member 65 substantially in a second direction, which may bea counter clockwise direction. In this manner, the drive control members26, 28 may be shifted asynchronously. FIG. 11 a shows the drive controlmember 26 shifted a distance X in the first direction and shows drivecontrol member 28 shifted in the second direction a distance Y. It isnoted that the slot 37 may be slightly curved to compensate fordifferences in actuating the locomotive drives 16, 18 due to hysteresisand other non-linear factors. However, any configuration of slot 37fashioned in the speed control members 54, 55 may be chosen with soundengineering judgment. Distance X may be greater than distance Y,representing that drive 16 has a greater magnitude of speed than drive18. In that the directions are opposite, the first wheel 6 may berotating forward at a speed proportionate to distance X and the secondwheel 7 may be rotating in reverse at a speed proportionate to distanceY, thus resulting in a turning radius that resides within the wheelbaseor at the center of the wheelbase. When the pedal member 41 is pivotedin the second direction 43 and with the steering in the same position,that is to say that forces F and F1 remain constant, the magnitude ofthe ratio of XJY remains the same although the direction of each driveis reversed. This results in proper steering in the forward and reversedirections as previously mentioned.

While specific embodiments of the invention have been described andillustrated, it is to be understood that these embodiments are providedby way of example only and that the invention is not to be construed asbeing limited thereto but only by proper scope of the following claims.

1. A steering and drive control mechanism for a zero turn radius vehiclethat includes a vehicle chassis and a pair of transmission systems forindependently driving at least two traction elements that are spacedfrom each other and each define two parallel drive directions fordriving said vehicle, said steering and drive control mechanismcomprising a drive assembly comprising a pivoting member mounted topivot about a pivot axis relative said chassis, a pair of controllinkage members engaged to the pivoting member in a movable manner sothat the connection point for each control linkage member with saidpivoting member can be moved relative said pivot axis, each said controllinkage member in operative connection with a respective transmissionsystems to control the respective transmission system, a foot operatedpedal assembly, operatively coupled to the drive assembly so thatmovement of the pedal assembly results in pivotal movement of thepivoting member about the pivot axis; a steering member pivotallyconnected to the vehicle chassis, a steering assembly coupling thesteering member with the control linkage members so that pivotingmovement of the steering member can vary the position of one or both ofthe connection points of the control linkage members relative the pivotaxis to thereby effect a change in operation of one of both of thetransmission systems.
 2. The steering and drive control mechanism asclaimed in claim 1 wherein the location of each of the connection pointsat the pivoting member of each of the control linkage members can bevaried by independently.
 3. The steering and drive control mechanism asclaimed in claim 1 wherein biasing means is provided to bias the controllinkage members to a location relative the pivoting member where thelocation of the connection points in the same distance from the pivotaxis.
 4. The steering and drive control mechanism as claimed in claim 1wherein each said control linkage member is mounted relative saidchassis by a mount that allow the control linkage member to displace ina manner rotationally unconstrained by said mount upon (a) the rotationof said pivoting member about the pivot axis and/or (b) movement of thesteering member to vary the position of one or both of the connectionpoints of the control linkage members relative the pivot axis.
 5. Thesteering and drive control mechanism as claimed in claim 1 wherein thetraction elements be wheels.
 6. The zero turning radius lawnmower thatincludes the mechanism as claimed in claim
 1. 7. The zero turning radiuslawnmower, said lawnmower comprising a pair of transmissions to drive atleast two drivers independently of each other; a chassis; a steering anddrive control mechanism as claimed in claim
 1. 8. The lawnmower asclaimed in claim 7 wherein the steering member is a steering wheel.
 9. Acontrol mechanism to control the speed and direction of travel of avehicle that includes a steering wheel and an accelerator pedal, saidvehicle capable of being propelled by two spaced apart traction elementseach independently driven by a respective motor, the output torque ofeach motor controlled by a displaceable input device, said controlmechanism comprising; a first push-pull rod having a first distal endand a second distal end, said first distal end engaged to said inputdevice of one of said motors (hereinafter “first motor”), a secondpush-pull rod having a first distal end and a second distal end, saidfirst distal end engaged to said input device of the other of saidmotors (hereinafter “second motor”), a pivot member mounted from saidvehicle pivotable about a pivot axis in a manner responsive to theposition of the accelerator pedal, said pivot member including at leastone lever arm to which and along at least part of which at least one ofsaid first and push-pull rod members and second push-pull rod memberscan traverse by being slidingly coupled thereto at or towards saidsecond distal end, such that when said pivot member is pivoted aboutpivot axis, the first push-pull rod can, when in at least one positionalong said lever arm, displace the input device of said first motor andsaid second push-pull rod can, when in at least one position along saidlever arm, displace the input device of said second motor, a firstcoupling member operatively extending between said steering wheel andsaid first push-pull rod and a second coupling member operativelyextending between said steering wheel and said second push-pull rod,wherein the movement of said steering wheel is, via said couplingmembers, capable of displacing both said first push-pull rod and saidsecond push-pull rod along said lever arm to displace first push-pullrod and/or said second push-pull rod relative said pivot axis to therebychange the effective lever arm effect of said pivot member on said firstpush-pull rod and/or said second push-pull rod and thereby vary itseffect on its respective input device.
 10. The mechanism as claimed inclaim 9 wherein the pivot member includes two lever arms, one for eachof said first push-pull rod and said second push-pull rod, each saidlever arm movable in unison.